A major source of electrical fires is arcing and/or resistance in wiring connections. Arcing in a wiring connection can occur when electrical current flows through poor electrical connections, such as due to loose screws, loose twist-on wire connectors, bad crimps, damaged wire insulation, corrosion, etc. Resistance in a wiring connection can also be caused by poor electrical connections, such as due to loose screws, loose twist-on wire connectors, bad crimps, damaged wire insulation, corrosion, damage to a wire due to arcing, etc.
Arcing in connections and high current flowing through resistive connections can create large localized heat sources. Such heat sources can degrade insulation which can increase arcing and result in heat sufficient to start a fire.